What is the most critical factor when operating a steam boiler?

Ensuring the correct water level in a steam boiler is crucial for safe and efficient operation. The water level must be maintained within specific limits to prevent two major issues. If the water level is too low, the boiler can experience a condition known as "dry firing," which can severely damage the boiler's components due to overheating. On the other hand, an excessively high water level can lead to water carryover into the steam lines, resulting in water hammer or damage to downstream equipment and processes.

Proper water level management involves regular monitoring and checking of gauge glasses and using automatic controls to maintain the level within safe operating parameters. The water feed system must also be reliable to compensate for steam production and ensure that adequate water is always supplied to the boiler. Thus, maintaining the correct water level is foundational to the safe and efficient operation of a steam boiler, making it the most critical factor among the options provided.